1 //===--- FunctionNamingCheck.cpp - clang-tidy -----------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "FunctionNamingCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "llvm/Support/Regex.h"
13 
14 using namespace clang::ast_matchers;
15 
16 namespace clang {
17 namespace tidy {
18 namespace google {
19 namespace objc {
20 
21 namespace {
22 
23 std::string validFunctionNameRegex(bool RequirePrefix) {
24   // Allow the following name patterns for all functions:
25   // • ABFoo (prefix + UpperCamelCase)
26   // • ABURL (prefix + capitalized acronym/initialism)
27   //
28   // If no prefix is required, additionally allow the following name patterns:
29   // • Foo (UpperCamelCase)
30   // • URL (capitalized acronym/initialism)
31   //
32   // The function name following the prefix can contain standard and
33   // non-standard capitalized character sequences including acronyms,
34   // initialisms, and prefixes of symbols (e.g., UIColorFromNSString). For this
35   // reason, the regex only verifies that the function name after the prefix
36   // begins with a capital letter followed by an arbitrary sequence of
37   // alphanumeric characters.
38   //
39   // If a prefix is required, the regex checks for a capital letter followed by
40   // another capital letter or number that is part of the prefix and another
41   // capital letter or number that begins the name following the prefix.
42   std::string FunctionNameMatcher =
43       std::string(RequirePrefix ? "[A-Z][A-Z0-9]+" : "") + "[A-Z][a-zA-Z0-9]*";
44   return std::string("::(") + FunctionNameMatcher + ")$";
45 }
46 
47 /// For now we will only fix functions of static storage class with names like
48 /// 'functionName' or 'function_name' and convert them to 'FunctionName'. For
49 /// other cases the user must determine an appropriate name on their own.
50 FixItHint generateFixItHint(const FunctionDecl *Decl) {
51   // A fixit can be generated for functions of static storage class but
52   // otherwise the check cannot determine the appropriate function name prefix
53   // to use.
54   if (Decl->getStorageClass() != SC_Static)
55     return FixItHint();
56 
57   StringRef Name = Decl->getName();
58   std::string NewName = Decl->getName().str();
59 
60   size_t Index = 0;
61   bool AtWordBoundary = true;
62   while (Index < NewName.size()) {
63     char ch = NewName[Index];
64     if (isalnum(ch)) {
65       // Capitalize the first letter after every word boundary.
66       if (AtWordBoundary) {
67         NewName[Index] = toupper(NewName[Index]);
68         AtWordBoundary = false;
69       }
70 
71       // Advance the index after every alphanumeric character.
72       Index++;
73     } else {
74       // Strip out any characters other than alphanumeric characters.
75       NewName.erase(Index, 1);
76       AtWordBoundary = true;
77     }
78   }
79 
80   // Generate a fixit hint if the new name is different.
81   if (NewName != Name)
82     return FixItHint::CreateReplacement(
83         CharSourceRange::getTokenRange(SourceRange(Decl->getLocation())),
84         llvm::StringRef(NewName));
85 
86   return FixItHint();
87 }
88 
89 } // namespace
90 
91 void FunctionNamingCheck::registerMatchers(MatchFinder *Finder) {
92   // This check should only be applied to Objective-C sources.
93   if (!getLangOpts().ObjC)
94     return;
95 
96   // Enforce Objective-C function naming conventions on all functions except:
97   // • Functions defined in system headers.
98   // • C++ member functions.
99   // • Namespaced functions.
100   // • Implicitly defined functions.
101   // • The main function.
102   Finder->addMatcher(
103       functionDecl(
104           unless(anyOf(isExpansionInSystemHeader(), cxxMethodDecl(),
105                        hasAncestor(namespaceDecl()), isMain(), isImplicit(),
106                        matchesName(validFunctionNameRegex(true)),
107                        allOf(isStaticStorageClass(),
108                              matchesName(validFunctionNameRegex(false))))))
109           .bind("function"),
110       this);
111 }
112 
113 void FunctionNamingCheck::check(const MatchFinder::MatchResult &Result) {
114   const auto *MatchedDecl = Result.Nodes.getNodeAs<FunctionDecl>("function");
115 
116   bool IsGlobal = MatchedDecl->getStorageClass() != SC_Static;
117   diag(MatchedDecl->getLocation(),
118        "%select{static function|function in global namespace}1 named %0 must "
119        "%select{be in|have an appropriate prefix followed by}1 Pascal case as "
120        "required by Google Objective-C style guide")
121       << MatchedDecl << IsGlobal << generateFixItHint(MatchedDecl);
122 }
123 
124 } // namespace objc
125 } // namespace google
126 } // namespace tidy
127 } // namespace clang
128